Analysis of two-channel generalized sidelobe canceller (GSC) with post-filtering

In this paper, we analyze a two-channel generalized sidelobe canceller with post-filtering in nonstationary noise environments. The post-filtering includes detection of transients at the beamformer output and reference signal, a comparison of their transient power, estimation of the signal presence probability, estimation of the noise spectrum, and spectral enhancement for minimizing the mean-square error of the log-spectra. Transients are detected based on a measure of their local nonstationarity, and classified as desired or interfering based on the transient beam-to-reference ratio. We introduce a transient discrimination quality measure, which quantifies the beamformer´s capability to recognize noise transients as distinct from signal transients. Evaluating this measure in various noise fields shows that desired and interfering transients can generally be differentiated within a wide range of frequencies. To further improve the transient noise reduction at low and high frequencies in case the signal is wideband, we estimate for each time frame a global likelihood of signal presence. The global likelihood is associated with the transient beam-to-reference ratios in frequencies, where the transient discrimination quality is high. Experimental results demonstrate the usefulness of the proposed approach in various car environments.